Latest news with #AtacamaCosmologyTelescope
Yahoo
21-03-2025
- Science
- Yahoo
A Telescope's Last Gasp Gives Us the Earliest Photos of the Universe
Before it shut down in 2022, a telescope in Chile captured one final gift for the world that has just been released: the universe's baby photos, just 380,000 years after the Big Bang. These freckled photos of the early universe, at an instant known as the Cosmic Microwave Background (CMB), are the farthest back in time we can look. Observing the Big Bang or immediately after is not possible, and not just because of technical limitations. Before the epoch shown in these images, the universe was so dense with plasma that light couldn't travel for more than a fraction of a millimeter without scattering off a proton or an electron. Everything just looked like a dense fog. Then the universe cooled enough to allow those charged particles to fuse into hydrogen and helium. Space opened up and became visible. The last photons from those first visible moments were preserved. The photons set off through space. All of them were stretched by the expansion of space around them. Some became further stretched out by gravitational wells around galaxy clusters. Others received an energy boost. The patterns of the evolving universe imprinted themselves on these ancient photons. Almost 14 billion years after their liberation, some of them hit the smooth white surface of a radio telescope located in the Atacama Desert of northern Chile. The Atacama Cosmology Telescope (ACT) is now closed for business. After 15 years of productive data releases, it saw its final light in 2022. However, the ACT team only recently released the polished versions of the telescope's last observations. These images not only show the most precise, high-resolution observations of the Cosmic Microwave Background but they also cover more of the sky than ever before. The red and blue speckles represent regions of over- and under-densities -- places where, 14 billion years ago, the universe had just a little more or less plasma. The new images confirm previous observations that the structure in the early universe maps onto its modern structure. Where there were slightly more photons in the primordial plasma now sit the most massive galaxy clusters. Fewer, and there's empty space. Einstein's theory of general relativity, which predicts how matter and light interact with one another at large scales, is one of the best substantiated theories in modern physics. It also causes problems. There appear to be four fundamental forces in nature: gravity, electromagnetism, weak, and strong. One set of physical laws known as the Standard model cohesively describes electromagnetism, the strong force, and the weak force. Gravity, though, has proven hard to mesh with the others. Discovering that general relativity isn't quite accurate is the grand hope of those searching for one theory of physics that unites all four forces. Perhaps then, a new model of gravity will appear out of the cracks, one that slots nicely into the Standard model. But general relativity has triumphed repeatedly so far, and the latest images from the ACT are no exception. "The amount by which light bends around dark matter structures is just as predicted by Einstein's theory of gravity," cosmologist Mathew Madhavacheril told Penn Today. Perhaps the most important part of these new observations is the detailed polarimetry. Polarimetry describes the measurement not just of how much light there is, or how much energy that light has, but in what direction the light is vibrating. Natural light is unpolarized, meaning that light waves traveling toward us may vibrate in any direction perpendicular to the line of travel. It's easy to change that by sticking a thin grating in front of the light, only allowing one vibrational direction through. That's how polarized sunglasses work. The polarization signal in the CMB sits at barely detectable thresholds. But ACT's new observations push past that threshold, and unlike the handful of other telescopes in the polarization game, they cover most of the sky. Polarization goes beyond the effects of gravity from massive structures like galaxies. Microscopic quantum density fluctuations can alter the polarization of light. Einstein's formulation of general relativity does not describe the quantum world. In fact, Einstein was uncomfortable with quantum mechanics and encouraged its proponents to better address its many peculiarities. While this leaves room for future physicists to etch their name in history, it would be a lot simpler if Einstein had just figured out everything for us. He didn't. General relativity on the quantum (read: atomic) scale continues to confound us, not least because testing it in the lab is fiendishly difficult. Fortunately, the new ACT data release is precise enough to contain clues about quantum gravity in its polarimetry. We just have to decode them.
New York Times
19-03-2025
- Science
- New York Times
‘More Than a Hint' That Dark Energy Isn't What Astronomers Thought
An international team of astronomers on Wednesday unveiled the most compelling evidence to date that dark energy — a mysterious phenomenon pushing our universe to expand ever faster — is not a constant force of nature but one that ebbs and flows through cosmic time. Dark energy, the new measurement suggests, may not resign our universe to a fate of being ripped apart across every scale, from galaxy clusters down to atomic nuclei. Instead, its expansion could wane, eventually leaving the universe stable. Or the cosmos could even reverse course, eventually doomed to a collapse that astronomers refer to as the Big Crunch. The latest results bolster a tantalizing hint from last April that something was awry with the standard model of cosmology, scientists' best theory of the history and the structure of the universe. The measurements, from last year and this month, come from a collaboration running the Dark Energy Spectroscopic Instrument, or DESI, on a telescope at Kitt Peak National Observatory in Arizona. 'It's a bit more than a hint now,' said Michael Levi, a cosmologist at Lawrence Berkeley National Laboratory and the director of DESI. 'It puts us in conflict with other measurements,' Dr. Levi added. 'Unless dark energy evolves — then, boy, all the ducks line up in a row.' The announcement was made at a meeting of the American Physical Society in Anaheim, Calif., and accompanied by a set of papers describing the results, which are being submitted for peer review and publication in the journal Physical Review D. 'It's fair to say that this result, taken at face value, appears to be the biggest hint we have about the nature of dark energy in the ~25 years since we discovered it,' Adam Riess, an astrophysicist at Johns Hopkins University and the Space Telescope Science Institute in Baltimore who was not involved in the work but shared the 2011 Nobel Prize in Physics for discovering dark energy, wrote in an email. But even as the DESI observations challenged the standard model of cosmology, a separate result has reinforced it. On Tuesday, the multinational team that ran the Atacama Cosmology Telescope in Chile released the most detailed images ever taken of the infant universe, when it was a mere 380,000 years old. (That telescope was decommissioned in 2022.) Their report, not yet peer-reviewed, seems to confirm that the standard model was operating as expected in the early universe. One element in that model, the Hubble constant, describes how fast the universe is expanding, but over the last half-century measurements of the constant have starkly disagreed, an inconsistency known as the Hubble tension. Theorists have mused that perhaps an additional spurt of dark energy in the very early universe, when conditions were too hot for atoms to form, could resolve this tension. The latest Atacama results seem to rule out this idea. But they say nothing about whether the nature of dark energy might have evolved later in time. Both reports evoked effusive praise from other cosmologists, who simultaneously confessed to a cosmic confusion about what it all meant. 'I don't think much is left standing as far as good ideas for what might explain the Hubble tension at this point,' said Wendy Freedman, a cosmologist at the University of Chicago who has spent her life measuring the universe and was not involved in either study. Michael Turner, a theorist at the University of Chicago, who was also not involved in the studies, said: 'The good news is, no cracks in the cosmic egg. The bad news is, no cracks in the cosmic egg.' Dr. Turner, who coined the term 'dark energy,' added that if there was a crack, 'it has not opened wide enough — yet — for us to clearly see the next big thing in cosmology.' Dark expectations Astronomers often compare galaxies in an expanding universe to raisins in a baking cake. As the dough rises, the raisins are carried farther apart. The farther they are from each other, the faster they separate. In 1998, two groups of astronomers measured the expansion of the universe by studying the brightness of a certain type of supernova, or exploding star. Such supernovas generate the same amount of light, so they appear predictably fainter at farther distances. If the expansion of the universe were slowing, as scientists believed at the time, light from faraway explosions should have appeared slightly brighter than foreseen. To their surprise, the two groups found that the supernovas were fainter than expected. Instead of slowing down, the expansion of the universe was actually speeding up. No energy known to physicists can drive an accelerating expansion; its strength should abate as it spreads ever more thinly across a ballooning universe. Unless that energy comes from space itself. This dark energy bore all the earmarks of a fudge factor that Albert Einstein inserted into his theory of gravity back in 1917 to explain why the universe was not collapsing under its own weight. The fudge factor, known as the cosmological constant, represented a kind of cosmic repulsion that would balance gravity and stabilize the universe — or so he thought. In 1929, when it became clear that the universe was expanding, Einstein abandoned the cosmological constant, reportedly calling it his biggest blunder. But it was too late. One feature of quantum theory devised in 1955 predicts that empty space is foaming with energy that would produce a repulsive force just like Einstein's fudge factor. For the last quarter-century, this constant has been part of the standard model of cosmology. The model describes a universe born 13.8 billion years ago, in a colossal spark known as the Big Bang, and composed of 5 percent atomic matter, 25 percent dark matter and 70 percent dark energy. But the model fails to say what dark matter or dark energy actually are. If dark energy really is Einstein's constant, the standard model portends a bleak future: The universe will keep speeding up, forever, becoming darker and lonelier. Distant galaxies will eventually be too far away to see. All energy, life and thought will be sucked from the cosmos. 'Something to go after' Astronomers on the DESI team are trying to characterize dark energy by surveying galaxies in different eras of cosmic time. Tiny irregularities in the spread of matter across the primordial universe have influenced the distances between galaxies today — distances that have expanded, in a measurable way, along with the universe. Data used for the latest DESI measurement consisted of a catalog of nearly 15 million galaxies and other celestial objects. Alone, the data set does not suggest that anything is awry with the theoretical understanding of dark energy. But combined with other strategies for measuring the expansion of the universe — for instance, studying exploding stars and the oldest light in the universe, emitted some hundred thousand years after the Big Bang — the data no longer lines up with what the standard model predicts. The discrepancy between data and theory is at most 4.2 sigma (in the units of uncertainty preferred by physicists), representing one in 50,000 chances that the results are a fluke. But the mismatch is not yet at five sigma (equal to one in 3.5 million chances), the stringent standard set by physicists to claim a discovery. Still, the disconnect is enticingly suggestive that something in the cosmological model is not well understood. Scientists might need to revise how they interpret gravity or make sense of the ancient light from the Big Bang. DESI astronomers think the problem could be the nature of dark energy. 'If we introduce a dynamical dark energy, then the pieces of the puzzle fit together better,' said Mustapha Ishak-Boushaki, a cosmologist at the University of Texas at Dallas who helped lead the latest DESI analysis. Will Percival, a cosmologist at the University of Waterloo in Ontario and a spokesperson for the DESI collaboration, expressed excitement about what lies on the horizon. 'This is actually a little bit of a shot in the arm for the field,' he said. 'Now we've got something to go after.' In the 1950s, astronomers claimed that only two numbers were needed to explain cosmology: one related to how fast the universe was expanding and another describing its deceleration, or how much that expansion was slowing down. Things changed in the 1960s, with the discovery that the universe was bathed in light from the Big Bang, known as the cosmic microwave background. Measuring this background radiation allowed scientists to investigate the physics of the early universe and the way that galaxies subsequently formed and evolved. As a result, the standard model of cosmology now requires six parameters, including the density of both ordinary and dark matter in the universe. As cosmology has become more precise, additional tensions have arisen between predicted and measured values of these parameters, leading to a profusion of theoretical extensions to the standard model. But the latest results from the Atacama Cosmology Telescope — the clearest maps to date of the cosmic microwave background — seem to slam the door on many of these extensions. DESI will continue collecting data for at least another year. Other telescopes, on the ground and in space, are charting their own views of the cosmos; among them are the Zwicky Transient Facility in San Diego, the European Euclid space telescope and NASA's recently launched SPHEREx mission. In the future, the Vera C. Rubin Observatory will begin recording a motion picture of the night sky from Chile this summer, and NASA's Roman Space Telescope is set to launch in 2027. Each will soak up the light from the sky, measuring pieces of the cosmos from different perspectives and contributing to a broader understanding of the universe as a whole. All serve as ongoing reminders of just what a tough egg the universe is to crack. 'Each of these data sets comes with its own strengths,' said Alexie Leauthaud, a cosmologist at the University of California, Santa Cruz, and a spokesperson for the DESI collaboration. 'The universe is complicated. And we're trying to disentangle a lot of different things.'
Yahoo
18-03-2025
- Science
- Yahoo
Universe's First Light Has Just Been Revealed in Stunning Detail
We just got the clearest snapshot yet of the first light that streamed through the Universe. After five years of staring unblinking at the sky, the Atacama Cosmology Telescope (ACT) has compiled the most detailed map we've ever seen of the cosmic microwave background – the faint light that permeates the Universe from just 380,000 years after the Big Bang. The results? We now have a clearer window into the infancy of the Universe, revealing with greater precision than ever how much mass exists in it, how large it is, and that the biggest crisis of cosmology – the Hubble constant – remains unresolved. The findings have been detailed in three preprint papers uploaded to arXiv and the Princeton University ACT website. "We are seeing the first steps towards making the earliest stars and galaxies," says physicist Suzanne Staggs of Princeton University in the US. "And we're not just seeing light and dark, we're seeing the polarization of light in high resolution. That is a defining factor distinguishing ACT from Planck and other, earlier telescopes." We can't see all the way back to the Big Bang. The early Universe was filled with a thick, murky, opaque fog of ionized plasma. This medium was impenetrable to light; any photons moving through the darkness simply scattered off free electrons. It wasn't until about 380,000 years after the Big Bang that these particles began to combine into neutral gas, mostly hydrogen, in what is known as the Epoch of Recombination. Once the free particles had been tucked away into atoms, light was able to spill forth, propagating throughout the Universe. That first light is the cosmic microwave background (CMB). As you can imagine, some 13.4 billion or so years later, the CMB is very, very faint and low in energy, so it takes a lot of observation time to detect it, and a lot of analysis to tease it out from amid all the other sources of light in the Universe. Compiling a map of the CMB has been the work of many decades, with the first all-sky map released in 2010, compiled from data collected by the Planck space telescope. Since then, scientists have been working to refine the map's resolution so we can learn more about how our Universe was born. This is what we have now with the latest data release from ACT, showing the intensity and polarization of the CMB with more clarity than ever. Polarization is the degree to which a light wave is rotated, which astronomers can decode to infer the nature of the environments the light has traveled through. "Before, we got to see where things were, and now we also see how they're moving," says Staggs. "Like using tides to infer the presence of the Moon, the movement tracked by the light's polarization tells us how strong the pull of gravity was in different parts of space." The CMB gives us a means of measuring the evolution of the Universe. We can look at the state of play now and at different times during the Universe's history, and compare it to the CMB to chart the 13.8 billion years since the Big Bang. "We've measured more precisely that the observable Universe extends almost 50 billion light-years in all directions from us," says cosmologist Erminia Calabrese of the University of Cardiff in the UK, "and contains as much mass as 1,900 'zetta-suns', or almost 2 trillion trillion Suns." Most of that mass is invisible. Normal baryonic matter makes up just 100 zetta-suns of the Universe's mass. That's everything we can detect – stars, galaxies, planets, people, black holes, gas, dust – all that stuff. Of this normal matter, 75 zetta-suns are hydrogen, and 25 zetta-suns are helium. The rest of the elements in the Universe combined have so little mass that they don't even make a dent in the pie chart. Another 500 zetta-suns make up invisible dark matter, the nature of which is unknown. The remaining 1,300 zetta-suns constitute dark energy, the name we give to the invisible force pushing space to expand faster than we can see. This brings us to the Hubble constant, which represents the expansion rate of the Universe. We go into the minutiae in more detail here, but the short version is that measurements of the distant Universe based on data such as the CMB show a slower expansion rate than measurements of the local Universe based on data such as supernovae. The former is around 67 or 68 kilometers per second per megaparsec, the latter around 73 or 74 kilometers per second per megaparsec. It's pretty fascinating, and worth reading about further if you have the inclination, but the upshot of this tension is that astronomers are trying to take better and better measurements of the Universe to try and close the gap between the two measurement ranges. The new map of the CMB gave a Hubble constant of 69.9 kilometers per second per megaparsec. It's one of the most rigorous measurements yet, and in good agreement with other values for the Hubble constant based on the CMB. "It was slightly surprising to us that we didn't find even partial evidence to support the higher value," Staggs says. "There were a few areas where we thought we might see evidence for explanations of the tension, and they just weren't there in the data." So that's still a problem that needs to be resolved. But the repeated, rigorous calculations seem to be increasingly hinting that either there's something crucial we're missing, or the Universe is quite a bit weirder than we thought. But that blobby, orange-and-blue map is bringing us closer to figuring it out, a testament to the insatiable curiosity and tireless ingenuity of human science. "We can see right back through cosmic history," says astrophysicist Jo Dunkley of Princeton University. "From our own Milky Way, out past distant galaxies hosting vast black holes, and huge galaxy clusters, all the way to that time of infancy." The three papers have been uploaded to arXiv and are available on the Princeton website. Incredible Video Shows Blood Moon Eclipse From Lunar Perspective Stranded NASA Astronauts Embrace Relief Crew in Joyous Scenes Incredible Image Reveals a Cosmic Hourglass Shimmering in Space
Yahoo
28-01-2025
- Science
- Yahoo
A cosmic 'CT scan' shows the universe is far more complex than expected
When you buy through links on our articles, Future and its syndication partners may earn a commission. A powerful combination of data from two very different astronomical surveys has allowed researchers to build a "cosmic CT scan" of the universe's evolution. These snapshots reveal that, as forces like gravity have reshaped the universe, the universe has in turn become less clumpy. In other words, the universe grew more complicated than expected. The team behind these findings used the sixth and final data release from the Atacama Cosmology Telescope (ACT) in combination with Year 1 data from the Dark Energy Spectroscopic Instrument (DESI) to reach these conclusions. This powerful combination of data allowed the researchers to layer cosmic time, akin to stacking ancient cosmic photographs over recent images of the universe, creating a multidimensional perspective of the cosmos. "This process is like a cosmic CT scan, where we can look through different slices of cosmic history and track how matter clumped together at different epochs," team co-leader Mathew Madhavacheril of the University of Pennsylvania said in a statement. "It gives us a direct look into how the gravitational influence of matter changed over billions of years." In order for the team to build this so-called CT scan of the universe, they needed to turn to light that has existed almost as long as the cosmos itself. With such ancient light, it's possible to track the changes the universe underwent as gravity reshaped it over around 13.8 billion years. "ACT, covering approximately 23% of the sky, paints a picture of the universe's infancy by using a distant, faint light that's been traveling since the Big Bang," team co-leader paper Joshua Kim, a graduate researcher in the Madhavacheril Group, said in the statement. "Formally, this light is called the Cosmic Microwave Background (CMB), but we sometimes just call it the universe's baby picture because it's a snapshot of when it was around 380,000 years old." The CMB is light left over from an event that happened shortly after the Big Bang called the "last scattering." This occurred when the universe had expanded and cooled enough to allow electrons and protons to form the first neutral atoms of hydrogen. The disappearance of free electrons meant that photons, aka particles of light, were free to travel without being endlessly scattered. In other words, the universe suddenly went from being opaque to being transparent. Today, that first light is seen as the CMB, also known as the "surface of last scattering." Though often described as a "cosmic fossil," the CMB hasn't remained entirely unchanged for billions of years. The expansion of the universe has caused its photons to shift to longer wavelengths and lose energy. Its temperature is now uniform at minus 454 degrees Fahrenheit (minus 270 degrees Celsius). Because mass warps the fabric of spacetime, giving rise to gravity, light from the CMB has warped while traveling past large, dense and heavy structures such as galaxy clusters. This is akin to looking at a grid pattern at the bottom of an empty swimming pool and noting the distortion caused as water is added. This process is known as "gravitational lensing." Albert Einstein first suggested it as part of his theory of gravity, general relativity. By noting how the CMB has warped and distorted over time, scientists can learn a great deal about the evolution of matter over billions of years. While the ACT data captures a snapshot of the CMB in its cosmic baby pictures, DESI provides scientists with a more recent record of a "grown-up" universe. DESI does this by mapping the universe's three-dimensional structure, achieved by mapping the distribution of millions of galaxies, particularly luminous red galaxies (LRGs). Using these galaxies as "cosmic landmarks," scientists can reconstruct how matter has dispersed over cosmic time."The LRGs from DESI are like a more recent picture of the universe, showing us how galaxies are distributed at varying distances," Kim said. "It's a powerful way to see how structures have evolved from the CMB map to where galaxies stand today."Putting together ACT CMB lensing maps and DESI LRG data is like browsing through a photo album showing the development of an infant to an adult, but for the cosmos. Browsing this cosmic photo album, the team noticed a small discrepancy. The "clumpiness" of matter the team calculated in later eras of the cosmos doesn't match theoretical the discrepancy isn't quite large enough to suggest entirely new physics are at play, it does suggest that cosmic structures haven't quite evolved in the way early-universe models would suggest. The results also hint that the universe's structural growth may have slowed in ways current models don't fully explain. "What we found was that, for the most part, the story of structure formation is remarkably consistent with the predictions from Einstein's gravity," Madhavacheril said. "We did see a hint for a small discrepancy in the amount of expected clumpiness in recent epochs, around four billion years ago, which could be interesting to pursue." Related Stories: — 'Mind-blowing' dark energy instrument results show Einstein was right about gravity — again — In a way, and the dark universe grew up together — Dark energy could be getting weaker, suggesting the universe will end in a 'Big Crunch' The researchers behind this work intend to continue this line of inquiry, but while utilizing more powerful upcoming telescopes, which should provide them with more precise measurements. The team's research was published on Dec. 10, 2024, in the Journal of Cosmology and Astroparticle Physics.
